Crude oil contains many different hydrocarbon compounds. The major compounds include petroleum gas, which includes small alkanes and alkenes (C1-C4), such as methane, ethane, propane, propylene, butane, and butylene; naphtha, which includes intermediate hydrocarbons (C5-C9); kerosene, a liquid mixture of C10-C18 alkanes and aromatics; diesel oil, which includes liquid alkanes containing twelve or more carbon atoms; lubricating oil, which includes long chain (C20-C50) alkanes, cycloalkanes, and aromatics; and fuel oil, which includes long chain (C20-C70) alkanes, cycloalkanes, and aromatics, along with various solid residuals such as coke, asphalt, tar, and waxes. The various hydrocarbon compounds are typically separated by fractional distillation.
Liquefied petroleum gas (also called LPG) refers to a flammable mixture of C1-C4 hydrocarbons that exists as a liquid at or below about −42° C., or when stored under pressure. At atmospheric pressure and temperatures above about −42° C., LPG is a colorless and odorless gas. As with natural gas, an identifying odorant, such as ethyl mercaptan, is typically added so that leaks of LPG can be more easily detected. Since LPG is substantially more compact as a liquid than as a gas, it is typically stored and transported under pressure (about 1725 kilopascals) where it exists as both a liquid and vapor.
Some LPG fuel systems include a filter to remove small particulate material from the fuel. However, a brown greasy or waxy material can still build up in the fuel system, for example, in the vaporizer (sometimes called a converter), downstream in the vapor hose, in the carburetor, and in the valves or mixer. The build-up is due to trace amounts of high molecular weight materials (also called greases, waxes or heavies) in the LPG acquired during refining, distribution and/or storage. When the LPG is vaporized, these high molecular weight materials can precipitate out of the vapor stream, often resulting in deposits that can obstruct injectors, valves, vaporizers or other components and can interfere with the operation of the fuel system. This can result in additional maintenance, shutdowns, and increased costs.
Therefore, a need exists for a system that can reduce the deposit of high molecular weight materials on LPG fuel system components while still removing particulate contaminants.